A stent is a tubular medical implement which is detained in the narrowed portion in question to ensure a required tubular region(space) by expanding the narrowed portion and the like when a tubular portion of a living body such as a blood vessel or other portions gets narrowed or clogged from obliteration. The stent is inserted into the body, with the diameter thereof small, and allowed to expand in the narrowed portion to make the diameter thereof large so that the tubular portion in question is expanded and kept in the expanded state.
The conventional stents, which are typically shown in FIGS. 11A, 11B and FIGS. 12A, 12B have the following problems. Incidentally, FIG. 11A and FIG. 12A are plan views showing the stents before expansion and FIG. 11B and FIG. 12B are plan views showing the stents after expansion.
In a stent 201 shown in FIG. 11A, a cell 206 constructing an annular unit 204 has a construction in which three straight line portions 207 are connected in parallel, and a curved portion 206A between each cell 206 is disposed opposite to the space 206B in the vicinity of another cell 206 constructing another annular unit 204. Because of such a construction, the stent has an appropriate radial support force (namely, as shown in FIG. 11B, a force to maintain an expansion state of the stent against the outer pressure in the direction from the blood vessel wall, when the stent is expanded and fixed on the blood vessel wall) and an excellent flexibility. On expanding or delivering of the stent, since the stent is inserted, moving along a curved line at a bent portion of the blood vessel, a portion of the cell 206 is sometimes jutted out and caught, which makes the delivery difficult (hereinafter, this is referred to as a flare phenomenon).
Meanwhile, in a stent 241 shown in FIG. 12A, cells 246 constructing an annular unit 244 have a construction in which approximately or substantially<shaped strut (a striate body) 247 is connected by a connecting part 245. Accordingly, it has the advantages that the stent is strong in radial support force, the approximately or substantially<shaped strut 247 never warps outward during expansion of the stent or when the stent passes through the bent portion of the blood vessel, and so on. However, it has a problem of shortage of flexibility. This is because there is only one bent portion in the connecting part 245 and the length of the connecting part 245 is short, as shown in FIG. 12A.
As described above, the conventional stent has a problem of not having both the flexibility and the radial support force keeping in balance.
As a result of assiduous studies to solve the above-described problem and to provide a stent having both the flexibility and the radial support force, the present inventors have reached the present invention.